The present invention relates to a thermal printer, and more particularly to a thermal printer which is provided with a temperature regulator which is effective for assuring reliable and consistent printing characteristics.
In general, thermal printers use thermosensitive paper or thermal transfer carbon ribbon to produce printed impressions. FIG. 1 is an example of a thermal transfer printer which uses thermal transfer carbon ribbon. A roll of thermal transfer carbon ribbon 1 is mounted on a feed spindle 2. Thermal carbon transfer ribbon 1 is supplied from and conveyed by guide roller 3, thermal print head 4, platen 4 and pinch rollers 6 until it reaches take-up spindle 7.
During printing, thermal transfer carbon ribbon 1 and label strip 8 are held between thermal print head 4 and platen 5 at which point heating elements 10 of thermal print head 4 heat up and cause carbon ink to be transferred from the ribbon onto label strip 8 in accordance with a pattern determined by certain printing signals. Label strip 8 is transferred out from feed spindle 11 and passes via thermal print head 4, platen 5 and guide roller 12 to take-up spindle 13.
Both the thermal paper or thermal ribbon types of thermal printers require a heating section of some type. Also needed is a temperature control means or circuit (not shown) to regulate the temperature in a printing zone 14.
However, if the printer is used for extended periods of time or under extreme ambient temperature conditions, unacceptable printing quality may be observed. For example, if the printer is located in an abnormally high ambient temperature region, the thermosensitive paper or the thermal carbon ribbon becomes too hot. The print is then smudged and in extreme cases the entire surface of the printing paper may be blackened completely during the printing process. In abnormally cold environments, for example in a cold storage warehouse or the like, it may be difficult to attain a minimum requisite printing temperature. This produces a blurred print.
The above problems arise with either thermosensitive paper or with thermal transfer carbon ribbon.